Diapositive 1

White et al. IJROBP 68:547-554. 2007

CBCT guidance for APBI

20 patients with

CBCT after skin-mark setup

and before treatment delivery

image registraton using

ipsilateral lung

and

external contours

random and systematic error were calculated and compared

Setup errors in mm

skin-mark setup

CBCT guidance*

systematic

2.7 1.7 2.4

0.8

0.7 0.8

random

2.4 2.2 2.9

1.5

1.5 1.6

isotropic CTV-PTVmargin

8.8

3.6

RL: right-left, AP: anterior-posterior, SI: superior-inferior, *3 mm action level (shifts > 3 mm are executed)

skin-mark setup

for APBI patients is sufficient for

1 cm CTV-PTV

margins

CBCT guidance

may permit a reduction of CTV-PTV margin

by a factor of 2